which is a linear combination of undivided differences of second-order
derivatives leads to give a fourth-order of accuracy, so this leads
to give a much smooth measurement than the global smoothness indicators
presented in [1]}, [2]}. The Taylor's expansion
of \(\eta \)  yields
\(\eta & =|-\frac{51}{384}\Delta x^{4}f_{j+\frac{1}{2}}^{(4)}+O(\Delta x^{5})|^{2},\\& =\Delta x^{8}(A+O(\Delta x)^{2}),\) 
